In general, a microphone that converts vibration energy generated by a sound pressure into electric energy or a speaker that converts electric energy into vibration energy includes a magnet constituting a magnetic circuit, and a diaphragm and a moving coil constituting a vibration system. Such a microphone or speaker is commonly called ‘dynamic type unit’.
FIG. 1 is a cross-sectional view illustrating the structure of a conventional microphone according to the prior art.
As shown in FIG. 1, when a diaphragm 103 vibrates upwardly and downwardly by a sound pressure indicated by arrows, a moving coil 111 disposed at the underside of the diaphragm 103 also moves upwardly and downwardly. Then, an N magnetic polarity formed at an upper portion of a magnetized magnet 108 and an S magnetic polarity formed at a lower portion of the magnet 108 form an S magnetic polarity around a plate 106 via a yoke 107 and a magnetic field MF1 is formed between the magnet 108 and the plate 106. Like this, the moving coil 111 moves upwardly and downwardly within the magnetic field MF1 to cause an electromagnetic induction to occur according to Faraday's law of induction. That is, an induced electromotive force is generated at both ends of the moving coil 111. In this case, as the waveform of the induced electromotive force becomes nearer a sinusoidal wave, a sound whose quality is closer to that of the original sound can be obtained.
A tone color reproduced by the microphone as shown in FIG. 1 is determined depending on the adjustment of the amount of air in a space A1 by means of a first filter 101, the adjustment of the amount of air to be discharged in a space A2 by means of a second filter 102, the adjustment of the amount of air to be discharged in a space A3 by means of a third filter 103, and the formation of a vortex of residual air within a reflective tank. In FIG. 1, non-explained reference numeral 100 denotes an upper cover and non-explained reference numeral 110 denotes a housing, respectively.
Also, FIG. 2 is a cross-sectional view illustrating the structure of a conventional speaker according to the prior art. As shown in FIG. 2, when an electrical signal is applied to a moving coil 111 between a plate 106 and a magnet 106/a pole 117, the moving coil 111 moves upwardly and downwardly to cause a diaphragm 103 to vibrate so as to discharge compress or discharge air in spaces A1, A2 and A3 to thereby reproduce an original sound.
It is important that a tone color of the speaker as shown in FIG. 2 is determined depending on the proper control of vibration of the diaphragm 103 by means of a spider 119, and the adjustment of the amount of air in the spaces A2 and A3 through lateral air holes 113. In FIG. 2, non-explained reference numeral 116 denotes a pole plate and non-explained reference numeral 118 denotes a bobbin, respectively.
In such a dynamic type unit, the induced electromotive force generated from the moving coil 111, i.e., sound quantity is determined depending on a gauss magnetic flux density of the magnet 108, a spacing between an N pole of the magnet 108 and an S pole of the plate 106, the number of windings of the moving coils 111, the thickness of a winding conductor, a change in resistance values, et. In addition, a frequency response is mostly determined depending on the thickness and material of the diaphragm 103, the shape of patterns engraved on the diaphragm 103 to facilitate the flow of sound pressure, etc.